Product formation of mycelial organisms, like Aspergillus niger, is intimately connected with their morphology. Pellet morphology is often requested for product formation. Therefore, it is important to reveal the influence of the hydrodynamic conditions on the morphological development. In the present study, pellet morphology and glucoamylase formation were studied under different agitation intensities of A. niger AB1.13. For pellet formation inside the bioreactor, without the use of precultures, it is necessary to work at low energy dissipation rates. Biomass growth and glucoamylase activity were correlated with energy dissipation. Furthermore, product yield was analysed in dependence of pellet size and concentration. The present work shows that simple equations based on Monod-kinetics can describe growth and product formation, in general, also in mycelian organisms. All measured morphological data, like pellet concentration, as well as glucoamylase formation, strongly depend on the hydrodynamic conditions.

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JournalApplied microbiology and biotechnology Members of the bacterial genus Sphingomonas are known to produce highly viscous polysaccharides in solution. The exopolysaccharide PS-EDIV was produced by Sphingomonas pituitosa strain DSM 13101, purified using centrifugation, and precipitation and its structure was elucidated by 1D and 2D NMR techniques and chemical microderivatization combined with various mass spectrometric techniques. The following repeating unit of the polysaccharide could be identified:In addition, the polysaccharide also contains acetyl and glyceryl groups whose exact positions were not determined. PS-EDIV is similar in structure to a known exopolysaccharide but differs in being the first bacterial polysaccharide in which two different glucuronic acids are combined. It caused a high viscosity of the culture broth after cultivation for 48 h, although a gelation was not observed.

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